In above-mentioned copending parent application Ser. No. 10/349,201, there is disclosed a polishing pad for use in chemical-mechanical polishing (CMP) of semiconductor wafers. The polishing pad thereof is made of a porous, fibrous structure bound by a thermoset resin and which is produced by a paper-making, wet laid process.
As in any polishing pad for use in CMP processes, the mechanical removal component is an important factor. However, there are some side effects associated with this mechanical component that also affect the chemical component of the CMP process and the chemical interactions associated therewith. Mechanical pad-properties have significant effects on polishing performance. Therefore, pads are manufactured for specific properties such as stiffness, roughness, compressive modulus, storage/loss modulus (viscoelastic behavior) and hydrophilic properties. Since polishing performance is measured by numerous metrics, modifying particular physical properties of the pad can affect more than one performance-characteristic.
There are many examples of prior-art CMP polishing pads that are a composite of two or more layers, in order to provide a polishing pad having different characteristics, such as hardness. Examples of such prior-art, multi-layer, CMP polishing pads are shown in U.S. Pat. Nos. 5,212,910, 5,257,478, 5,287,663, 6,210,254, and 6,383,066.